위의 메뉴처럼 색상을 바꾸고 싶습니다. 메뉴 선택하면 저렇게 하얀바탕에 저런식으로 바뀌도록요.

참고로 테마는 company 테마 사용하고있습니다. 

조금만 바꾸면 될것같은데.. 처음 만들어보는거라서 너무 힘드네요. 고수님들 도와주세요.

/* 상단 레이아웃 */
#hd {z-index:4;position:absolute;top:0px;left:0;min-width:1000px;width:100%;}
.hd_zindex {z-index:10 !important}
#hd_h1 {position:absolute;font-size:0;line-height:0;overflow:hidden}
#hd_wrapper {margin:40px auto;height:55px;width:1000px;zoom:1;background:#3c95d5;position:relative}
#hd_wrapper:after {display:block;visibility:hidden;clear:both;content:""}
#logo {float:left;padding:0;background:#4375DB;height:55px;width:150px;padding-left:20px}
#logo a{display:inline-block;vertical-align:middle;margin-top:13px}

/*상단_로그인*/
#tnb {position:Absolute;top:-30px;right:0;}
#tnb:after {display:block;visibility:hidden;clear:both;content:""}
#tnb li{float:left;border:1px solid #3c95d5;padding:3px; margin-left:3px;border-radius:3px;font-size:0.917em;background:#3c95d5 }
#tnb li a{color:#fff;}
#tnb li.tnb_adm{background:#fff;}
#tnb li.tnb_adm a{color:#3c95d5;}

/* 메인메뉴*/
#gnb {position:relative;margin: 0;float:left}
#gnb:after {display:block;visibility:hidden;clear:both;content:""}
#gnb h2 {position:absolute;font-size:0;line-height:0;overflow:hidden}
#gnb_1dul {padding:0;zoom:1;}
#gnb_1dul:after {display:block;visibility:hidden;clear:both;content:""}
.gnb_1dli {z-index:10;position:relative;float:left;width:117px;text-align:center;}
a.gnb_1da {padding-right:10px;display:inline-block;  text-overflow: ellipsis;  overflow: hidden;  white-space: nowrap;font-weight:bold;line-height:2.95em;text-decoration:none;color:#fff;height:55px;line-height:55px;display:block;font-size:1.17em}
a.gnb_bg{background:url('../img/gnb_bg.gif') 100px 50%  no-repeat;}
.gnb_bg:focus, .gnb_bg:hover {background-color:#312f46 ;text-decoration:none}
.gnb_1dli_air .gnb_1da {background-color:#3c95d5;color:#fff}
.gnb_1dli_on .gnb_1da {background-color:#3c95d5;color:#4FC9DE}
.gnb_2dul {display:none;position:absolute;top:55px;width:180px;left:0}
.gnb_2da {display:block;padding:13px 10px;text-align:left;text-decoration:none;}
.gnb_1dli_air .gnb_2da {background-color:#3c95d5;color:#FFF}
.gnb_1dli_on .gnb_2da {background-color:#3c95d5;color:#FFF}
.gnb_2da:focus, .gnb_2da:hover {background:#00C6ED;text-decoration:none}
.gnb_1dli_over .gnb_2dul {display:block;left:0;background:#fff}
.gnb_1dli_over2 .gnb_2dul {display:block;right:0;background:#fff}